Resin composition and molded product thereof

ABSTRACT

Provided is a resin composition configured to show a small change in the void ratio of hollow resin particles during mold processing and configured to stably mold a lightweight molded product having a small variation in specific gravity. The resin composition is a resin composition comprising 50 parts by mass to 95 parts by mass of a thermoplastic elastomer and 5 parts by mass to 50 parts by mass of hollow resin particles, wherein the hollow resin particles have a void ratio of from 50% to 85%; wherein the hollow resin particles have a shell containing a resin; and wherein, with respect to 100 parts by mass of repeating units constituting the resin, 30 parts by mass to 100 parts by mass of a crosslinkable monomer unit and 0 part by mass to 70 parts by mass of a non-crosslinkable monomer unit are contained as a polymerizable monomer unit.

TECHNICAL FIELD

The disclosure relates to a resin composition and a molded productthereof.

BACKGROUND ART

In the process of automobile assembly, thermoplastic or thermosettingmolding resins as typified by polyvinyl chloride (PVC), urethane, epoxy,etc., have been used.

The recent trend of growing awareness to environmental problems such asglobal warming and air pollution, has increased the demand for reducingthe weight of automobiles to improve their fuel efficiency. Thus,automobile manufacturers have been trying to reduce the weight ofautomotive parts, as well as the weight of molding resins.

Patent Literature 1 discloses that an expanded molded product havingexcellent dispersibility of thermally expandable microspheres and astable expansion ratio, is produced from a masterbatch, and athermoplastic elastomer and the thermally expandable microspheres areincluded the masterbatch, the thermoplastic elastomer having an Ahardness of 15 to 54, and the thermally expandable microspheres beingcomposed of an outer shell, which is made of a thermoplastic resin, anda foaming agent, which is enveloped by the outer shell and vaporizeswhen heated.

A lightweight thermoplastic resin composition having exceptionalflexibility and adequate anti-slip properties is disclosed in PatentLiterature 2, the composition containing glass balloons and athermoplastic elastomer.

CITATION LIST Patent Literatures

Patent Literature 1: U.S. Pat. No. 6,182,004

Patent Literature 2: International Publication No. WO2016/104306

SUMMARY OF INVENTION Technical Problem

The masterbatch disclosed in Patent Literature 1, which includes thethermally expandable microspheres and the thermoplastic elastomer, hasthe following problem: obtaining a molded product having a smallvariation in specific gravity, is likely to be difficult since theexpansion ratio of the masterbatch including the thermally expandablemicrospheres and the thermoplastic elastomer disclosed in PatentLiterature 1, varies depending on a difference in the temperature orpressure condition of molding, and the thermoplastic elastomer iselastic.

The glass balloons disclosed in Patent Literature 2 have the followingproblem: since they are a material having high specific gravity, theyprovide insufficient weight reduction of parts.

In light of the above circumstances, an object of the present disclosureis to provide a resin composition configured to show a small change inthe void ratio of hollow resin particles during mold processing andconfigured to stably mold a lightweight molded product having a smallvariation in specific gravity.

Solution to Problem

The present disclosure provides a resin composition comprising 50 partsby mass to 95 parts by mass of a thermoplastic elastomer and 5 parts bymass to 50 parts by mass of hollow resin particles,

wherein the hollow resin particles have a void ratio of from 50% to 85%;

wherein the hollow resin particles have a shell containing a resin; and

wherein, with respect to 100 parts by mass of repeating unitsconstituting the resin, 30 parts by mass to 100 parts by mass of acrosslinkable monomer unit and 0 part by mass to 70 parts by mass of anon-crosslinkable monomer unit are contained as a polymerizable monomerunit.

According to the resin composition of the present disclosure, the hollowresin particles preferably do not exhibit a glass transition temperaturein a range of from 0° C. to 250° C.

According to the resin composition of the present disclosure, the hollowresin particles preferably have a volume-based average particle diameterof from 1.0 μm to 20.0 μm.

The present disclosure provides a molded product comprising the resincomposition.

Advantageous Effects of Invention

According to the present disclosure, the resin composition configured toshow a small change in the void ratio of the hollow resin particlesduring mold processing and configured to stably mold a lightweightmolded product having a small variation in specific gravity, can beprovided.

BRIEF DESCRIPTION OF DRAWINGS

In the accompanying drawings,

FIG. 1 is a schematic diagram showing an embodiment of a method forproducing hollow resin particles used in the present disclosure;

FIG. 2 is a schematic diagram showing an embodiment of a suspension in asuspension preparation step; and

FIG. 3 is a schematic diagram showing a dispersion for conventionalemulsion polymerization.

DESCRIPTION OF EMBODIMENTS

The present disclosure provides a resin composition comprising 50 partsby mass to 95 parts by mass of a thermoplastic elastomer and 5 parts bymass to 50 parts by mass of hollow resin particles,

wherein the hollow resin particles have a void ratio of from 50% to 85%;

wherein the hollow resin particles have a shell containing a resin; and

wherein, with respect to 100 parts by mass of repeating unitsconstituting the resin, 30 parts by mass to 100 parts by mass of acrosslinkable monomer unit and 0 part by mass to 70 parts by mass of anon-crosslinkable monomer unit are contained as a polymerizable monomerunit.

The shell of the hollow resin particles contained in the resincomposition of the present disclosure, is the resin in which theproportion of the crosslinkable monomer is high. Accordingly, the shellhas low thermoplasticity, and the mechanical strength of the hollowresin particles is high even at high temperature. Also, since the hollowresin particles do not include an included agent, they are not likely toexpand even when they are heated. Accordingly, the hollow resinparticles are not likely to cause a collapse by external force, causeexpansion by an increase in internal pressure, etc., at hightemperature. As a result, the hollow resin particles are not likely tocollapse in a high-temperature and high-pressure environment during themold processing of the resin composition; the hollow resin particlesshow a small change in the void ratio; and a molded product having asmall variation in specific gravity, can be obtained. Also, the hollowresin particles are lightweight particles due to their high void ratio.

According to the resin composition of the present disclosure, alightweight molded product having a small variation in specific gravity,that is, a molded product in which the specific gravities of themoieties are uniformized, can be stably molded since a molded productwith a certain void ratio can be obtained irrespective of moldprocessing conditions such as extrusion molding and injection molding.

The reason for the small specific gravity variation of the moldedproduct is estimated as follows. Even when a difference occurs in thetemperature of the moieties of the resin composition during the moldingprocess or in the time of cooling the moieties, a change in the volumeof the hollow resin particles dispersed in the resin composition, issmall. Accordingly, even when a pressure is applied to the resincomposition during the molding of the composition and is then decreasedto normal pressure after the resin composition is molded, the volume ofthe thus-obtained molded product is less likely to change. As a result,it is estimated that a difference in the specific gravity between themoieties of the molded product, is less likely to occur.

Due to the above reasons, the resin composition of the presentdisclosure offers a wide range of selectable mold processing conditions.

The resin composition of the present disclosure comprises 50 parts bymass to 95 parts by mass of a thermoplastic elastomer and 5 parts bymass to 50 parts by mass of hollow resin particles. The upper limit ofthe thermoplastic elastomer is preferably 90 parts by mass or less, andthe lower limit of the hollow resin particles is preferably 10 parts bymass or more.

In general, an elastomer means a material characterized in that whenexternal force is applied thereto, it instantly deforms depending on theexternal force, and when it is released from the external force, it goesback to the original shape in a short time.

In general, a thermoplastic elastomer is characterized in that itexhibits rubber elasticity at normal temperature)(25° C. and isplasticized and molded at high temperature.

In the present disclosure, typically, such a material can be used as thethermoplastic elastomer, that when the original size is determined as100%, it can be deformed up to 200% at room temperature (20° C.) by asmall external force, and when it is released from the external force,the size returns to less than 130%. In particular, the small externalforce means an external force having a tensile strength of from 1 MPa to100 MPa. More specifically, the following polymer can be used as thethermoplastic elastomer: based on the permanent set testing of JIS K6262-1997, in a tensile test at 20° C., a specimen in the dumbbell No. 4shape defined in JIS K 6251-1993 can be extended twice the gauge lengthbefore extension, and in the case where the specimen is extended twicethe gauge length before extension and retained in that state for 60minutes, it exhibits a permanent set of less than 30% 5 minutes after itis released from the tensile external force.

As the thermoplastic elastomer, a thermoplastic elastic polymer that hasbeen used as a molding resin, may be used. As the thermoplasticelastomer, examples include, but are not limited to, a urethane-basedelastomer, a styrene-based elastomer, an olefin-based elastomer, anamide-based elastomer and an ester-based elastomer. Due to theirexcellent heat resistance, an olefin-based elastomer, an amide-basedelastomer and an ester-based elastomer are preferred.

As the urethane-based elastomer, examples include, but are not limitedto, “PANDEX” manufactured by DIC Corporation, “MIRACTRAN E390”manufactured by Nippon Miractran Co., Ltd., “PARAPREN” manufactured byNippon Polyurethane Industry Co., Ltd., and “DESMOPAN” manufactured bySumitomo Bayer Urethane Co., Ltd.

As the styrene-based elastomer, examples include, but are not limitedto, a block copolymer such as a styrene-butadiene-styrene (SBS)copolymer, a styrene-isoprene-styrene (SIS) copolymer, astyrene-ethylene-butylene-styrene (SEBS) copolymer, astyrene-ethylene-propylene-styrene (SEPS) copolymer and astyrene-butadiene-butylene-styrene (SBBS) copolymer.Commercially-available styrene-based elastomer products include thefollowing, for example: “RABALON 7400B” manufactured by MitsubishiChemical Corporation; “TUFBRENE”, “ASABRENE” and “TUFTEC” manufacturedby Asahi Kasei Corporation; “ELASTOMER AR” manufactured by ARONKASEICo., Ltd.; “SEPTON” and “HYBRAR” manufactured by Kuraray Co., Ltd.; “JSRTR” and “JSR SIS” manufactured by JSR Corporation; “MAXIRON”manufactured by Showa Kasei Kogyo Co., Ltd.; “TRI-BLENE” and “SUPERTRI-BLENE” manufactured by Shinko Kasei Co., Ltd.; “ESPOLEX SB SERIES”manufactured by Sumitomo Chemical Company, Ltd.; and “LEOSTOMER”,“ACTYMER”, “HYPER-ALLOY ACTYMER” and “ACTYMER G” manufactured by RikenTechnos Corporation.

As the olefin-based elastomer, examples include, but are not limited to,an ethylene-acrylic acid copolymer, an ethylene-propylene-dienecopolymer, an ethylene-vinyl acetate copolymer, polybutene, andchlorinated polyethylene. Commercially-available olefin-based elastomerproducts include the following, for example: “SANTOPRENE” and“VISTAMAXX” manufactured by Exxon Mobil Corporation; “EXCELINK”manufactured by JSR Corporation; “MAXIRON” manufactured by Showa KaseiKogyo Co., Ltd.; “ESPOLEX TPE SERIES” manufactured by Sumitomo ChemicalCompany, Ltd.; “ENGAGE” manufactured by Dow Chemical Japan Ltd.; “PRIMETPO” manufactured by Prime Polymer Co., Ltd.; “MILASTOMER” manufacturedby Mitsui Chemicals, Inc.; “ZELAS” and “THERMORUN” manufactured byMitsubishi Chemical Corporation; and “MULTIUSE LEOSTOMER”, “OLEFLEX” and“TRINITY FR” manufactured by Riken Technos Corporation.

Commercially-available ester-based elastomer products include thefollowing, for example: “PREMALLOY” manufactured by Mitsubishi ChemicalCorporation, “PELPRENE” manufactured by Toyobo Co., Ltd., and “HYTREL”manufactured by DuPont-Toray Co., Ltd.

As the amide-based elastomer, examples include, but are not limited to,“UBE POLYAMIDE ELASTOMER PAE” manufactured by UBE Industries, Ltd.,“GRILAX A” manufactured by Dainippon Ink and Chemicals Incorporated, and“NOVAMID PAE” manufactured by Mitsubishi Engineering-PlasticsCorporation.

[Hollow Resin Particle]

In the present disclosure, the “hollow resin particle” means a resinparticle which has a shell containing a resin (an outer shell portion)and which generally has one or two or more hollow portions filled withvacuum or gas.

In the present disclosure, the “hollow portion” means a portion of theinterior of a particle occupied by a hollow. Whether a particle has ahollow portion or not can be determined by, for example, SEM observationof a cross section of the relevant particle or TEM observation of therelevant particle as it is.

The resin shell (the outer shell portion) of the particle may not have acommunication hole, and the “hollow portion” in the present disclosuremay be isolated from the outside of the particle by the shell of theparticle.

The resin shell of the particle may have one or two or morecommunication holes, and the “hollow portion” in the present disclosuremay communicate with the outside of the particle via the communicationhole.

In the present disclosure, the “hollow” means a space which issurrounded by the shell and which can be filled with a highly fluidmedium such as liquid and gas. That is, it means a so-called void state.

The void ratio of the hollow resin particle can be reworded as thevolume ratio occupied by the hollow portion of the hollow resinparticle.

For the void ratio of the hollow resin particle, the lower limit is 50%or more, preferably 53% or more, more preferably 55% or more, still morepreferably 58% or more, and particularly preferably 62% or more. Whenthe void ratio of the hollow resin particle is 50% or more, since theratio occupied by the hollow portion is high, the hollow resin particlescan achieve weight reduction. For the void ratio of the hollow resinparticle, the upper limit is 85% or less. From the viewpoint ofmaintaining the strength of the hollow resin particle, the upper limitis preferably 84% or less, more preferably 83% or less, still morepreferably 81% or less, and particularly preferably 78% or less.

The void ratio of the hollow resin particle is calculated as follows, onthe basis of the following formula (0). The apparent density D₁ wasdivided by the true density D₀. The resultant was multiplied by 100, andthe value thus obtained was subtracted from 100, thereby obtaining thevoid ratio of the particle.

Void ratio (%)=100−[Apparent density D ₁]/[True density D₀]×100  Formula (0)

A method of measuring the apparent density D₁ of the hollow resinparticle is as follows. First, approximately 30 cm³ of hollow resinparticles are introduced into a measuring flask with a volume of 100cm³, and the mass of the introduced hollow resin particles is preciselyweighed. Next, the measuring flask in which the hollow resin particlesare introduced is precisely filled with isopropanol up to the markedline while care is taken so that air bubbles do not get in. The mass ofthe isopropanol added to the measuring flask is precisely weighed, andthe apparent density D₁ (g/cm³) of the hollow resin particle iscalculated on the basis of Formula (I) mentioned below.

Apparent density D ₁=[Mass of the hollow resin particles]/(100−[Mass ofthe isopropanol]/[Specific gravity of the isopropanol at the measuringtemperature])  Formula (I)

The apparent density D₁ is equivalent to the specific gravity of thewhole hollow resin particle in the case where the hollow portion isregarded as part of the hollow resin particle.

A method of measuring the true density D₀ of the hollow resin particleis as follows. Hollow resin particles are pulverized in advance; then,approximately 10 g of pulverized pieces of hollow resin particles areintroduced into a measuring flask with a volume of 100 cm³, and the massof the introduced pulverized pieces is precisely weighed. After that,similarly to the measurement of the apparent density mentioned above,isopropanol is added to the measuring flask, the mass of the isopropanolis precisely weighed, and the true density D₀ (g/cm³) of the hollowresin particle is calculated on the basis of Formula (II) mentionedbelow.

True density D ₀=[Mass of the pulverized pieces of the hollow resinparticles]/(100−[Mass of the isopropanol]/[Specific gravity of theisopropanol at the measuring temperature])  Formula (II)

The true density D₀ is equivalent to the specific gravity of the shellportion alone of the hollow resin particle. As is clear from themeasurement method mentioned above, when calculating the true densityD₀, the hollow portion is not regarded as a part of the hollow resinparticle.

The hollow resin particles preferably do not exhibit a glass transitiontemperature (Tg) in a range of from 0° C. to 250° C. Since the hollowresin particles do not exhibit a glass transition temperature (Tg) in arange of from 0° C. to 250° C., it is considered that the hollow resinparticles are not likely to deform and collapse when heated.

The glass transition temperature can be measured by differentialscanning calorimetry (DSC).

For the volume-based average particle diameter (volume average particlediameter) of the hollow resin particles, the lower limit is preferably1.0 μm or more, more preferably 1.3 μm or more, still more preferably1.6 μm or more, particularly preferably 2.0 μm or more, and mostpreferably 2.3 μm or more. The upper limit is preferably 20.0 μm orless, more preferably 16.0 μm or less, still more preferably 12.0 μm orless, particularly preferably 9.0 μm or less, and most preferably 6.5 μmor less.

When the volume average particle diameter of the hollow resin particleis 1.0 μm or more, the desired void ratio is obtained. Accordingly, thehollow resin particles can achieve weight reduction. Further, when thevolume average particle diameter of the hollow resin particles is 20.0μm or less, since the hollow resin particles are not likely to collapse,the hollow resin particles have high compressive strength.

The number average particle diameter of the hollow resin particles isgenerally from 0.1 μm to 20.0 μm.

The particle size distribution (the volume average particle diameter(Dv)/the number average particle diameter (Dn)) of the hollow resinparticles is not particularly limited. For example, it may be from 1.00to 2.50. It is more preferably from 1.01 to 1.80, still more preferablyfrom 1.02 to 1.40, particularly preferably from 1.03 to 1.35, mostpreferably from 1.04 to 1.28. When the particle size distribution is2.50 or less, particles which have low dispersion in compressivestrength characteristics and heat resistance among the particles can beobtained. Further, when the particle size distribution is 2.50 or less,for example, a product having uniform thickness can be produced whenproducing a product such as a molded product.

The volume average particle diameter (Dv) and the number averageparticle diameter (Dn) of the hollow resin particles can be found by,for example, using a laser diffraction particle size distributionmeasuring apparatus, measuring the particle diameter of each hollowresin particle and calculating the number average and the volume averageof them, the obtained values can be the number average particle diameter(Dn) and the volume average particle diameter (Dv) of the particles,respectively. The particle size distribution is found by dividing thevolume average particle diameter by the number average particlediameter.

The shell of the hollow resin particles contains a resin.

The polymerizable monomer, which is a raw material for the resin,contains a crosslinkable monomer. As needed, it contains anon-crosslinkable monomer.

In the present disclosure, the non-crosslinkable monomer means acompound having only one polymerizable functional group. For example, atleast one monomer selected from the group consisting of a monovinylmonomer and a hydrophilic monomer, can be used.

In the present disclosure, the monovinyl monomer means a compound havingone polymerizable carbon-carbon double bond, and a compound other thanthe hydrophilic monomer described later. A resin containing a monovinylmonomer unit is generated by polymerization of a monovinyl monomer.

The compound having one polymerizable carbon-carbon double bond is thecarbon-carbon double bond itself, or it is a compound having a groupcontaining a carbon-carbon double bond, such as a compound containing avinyl group, an acrylic group, a methacrylic group, an ethylene groupand an allyl group, for example. Examples of the monovinyl monomerinclude an acrylic-based monovinyl monomer such as (meth)acrylate; anaromatic monovinyl monomer such as styrene, vinyltoluene andα-methylstyrene; and a mono-olefin monomer such as ethylene, propyleneand butylene.

In the present disclosure, (meth)acrylate means acrylate ormethacrylate. Examples of (meth)acrylate include methyl (meth)acrylate,ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate,lauryl (meth)acrylate, glycidyl (meth)acrylate and 2-hydroxyethyl(meth)acrylate. (Meth)acrylic acids and (meth)acrylates may be usedalone or in combination of two or more kinds.

Among the (meth)acrylates described above, preferably, at least oneselected from the group consisting of butyl acrylate and methylmethacrylate is used.

Thus, by using a monomer which is resistant to relatively hightemperature conditions such as (meth)acrylate, the heat resistance ofthe obtained hollow resin particle can be enhanced as compared to, forexample, the case where a monomer having a nitrile group is used.

In the present disclosure, the hydrophilic monomer means a monomersoluble in water, and more specifically means a monomer having asolubility in water of 1% by mass or more. Using a hydrophilic monomerfor the polymerization to obtain the resin is preferable particularly interms of less aggregation of the obtained hollow resin particles. Thepolymerizable functional group of the hydrophilic monomer may be acarbon-carbon double bond itself, or it may be a group containing acarbon-carbon double bond.

The resin contained in the hollow resin particle may contain, as ahydrophilic monomer unit, for example, a carboxyl group-containingmonomer unit, a hydroxyl group-containing monomer unit, an amidegroup-containing monomer unit and a polyoxyethylene group-containingmonomer unit. Among them, it is preferable that the resin contains acarboxyl group-containing monomer unit, since particles with high heatresistance can be obtained. Further, the case where the resin contains ahydroxyl group-containing unit is preferable in the effect by use of thehydrophilic monomer, that is, using a hydrophilic monomer forpolymerization to obtain the resin is preferable particularly in theeffect of less aggregation of the obtained hollow resin particles.

Examples of the carboxyl group-containing monomer include a(meth)acrylic acid monomer and a maleic acid monomer. In the presentdisclosure, (meth)acrylic acid means acrylic acid or methacrylic acid.Especially, in the case where (meth)acrylic acid and the above-mentioned(meth)acrylate are used in combination, a preferred mass ratio is(meth)acrylic acid:(meth)acrylate=100:0 to 30:70, and a more preferredmass ratio is (meth)acrylic acid:(meth)acrylate=100:0 to 35:65.

Examples of the hydroxyl group-containing monomer include a2-hydroxyethyl acrylate monomer, a 2-hydroxyethyl methacrylate monomer,a 2-hydroxypropyl acrylate monomer, a 2-hydroxypropyl methacrylatemonomer, and a 4-hydroxybutyl acrylate monomer.

Examples of the amide group-containing monomer include an acrylamidemonomer and a dimethylacrylamide monomer.

Examples of the polyoxyethylene group-containing monomer include amethoxypolyethylene glycol acrylate monomer and a methoxypolyethyleneglycol methacrylate monomer.

In the present disclosure, the crosslinkable monomer means a compoundhaving two or more polymerizable functional groups. The mechanicalcharacteristics of the obtained copolymer shell can be enhanced by usingthe crosslinkable monomer. Further, since the crosslinkable monomer hasa plurality of polymerizable functional groups, the monovinyl monomerand the hydrophilic monomer and so on described above can be linkedtogether, particularly the heat resistance of the obtained hollow resinparticle can be enhanced. Examples of the polymerizable functionalgroups include a carbon-carbon double bond itself or a group containinga carbon-carbon double bond.

The crosslinkable monomer is not particularly limited, as long as it hastwo or more polymerizable functional groups. Examples of thecrosslinkable monomer include: aromatic divinyl compounds such asdivinyl benzene, divinyl naphthalene, diallyl phthalate and derivativesthereof; ester compounds such as allyl (meth)acrylate, ethylene glycoldi(meth)acrylate and diethylene glycol di(meth)acrylate, in which two ormore compounds having a carbon-carbon double bond are esterified to acompound having two or more hydroxyl groups or carboxyl groups; otherdivinyl compounds such as N,N-divinylaniline and divinyl ether. Amongthem, at least one of divinyl benzene and ethylene glycoldi(meth)acrylate is preferred.

With respect to 100 parts by mass of the repeating units constitutingthe resin, the content ratio of the crosslinkable monomer unit may befrom 30 parts by mass to 100 parts by mass. The lower limit ispreferably 35 parts by mass or more, more preferably 40 parts by mass ormore, and still more preferably 45 parts by mass or more. The upperlimit is preferably 90 parts by mass or less, more preferably 85 partsby mass or less, and still more preferably 80 parts by mass or less.When the content of the crosslinkable monomer contained is from 30 partsby mass to 100 parts by mass, the obtained hollow resin particles arenot likely to be dented, so that the void ratio of the hollow resinparticle can be maintained at a high level.

Meanwhile, with respect to 100 parts by mass of the repeating unitsconstituting the resin, the content ratio of the non-crosslinkablemonomer unit may be 0 part by mass to 70 parts by mass. The lower limitis preferably 3 parts by mass or more, more preferably 10 parts by massor more, still more preferably 15 parts by mass or more, andparticularly preferably 20 parts by mass or more. The upper limit ispreferably 65 parts by mass or less, more preferably 60 parts by mass orless, still more preferably 55 parts by mass or less, and particularlypreferably 45 parts by mass or less.

The content ratio of the crosslinkable monomer unit or thenon-crosslinkable monomer unit is determined, for example, bycalculating the ratio of the crosslinkable monomer subjected to thepolymerization reaction, from the charged amount of the crosslinkablemonomer at the time of polymerization and the remained amount of thecrosslinkable monomer at the end of the polymerization.

To control the physical properties of the particle, in addition to thecrosslinkable monomer unit or the non-crosslinkable monomer unit, theresin constituting the hollow resin particles may contain a monomer unitderived from a monomer other than the crosslinkable monomer unit or thenon-crosslinkable monomer unit in the main chain or side chain, or anyfunctional group may be modified on the polymer chain. For example, theresin constituting the hollow resin particle may be urethane-acrylicresins from the viewpoint of excellent heat insulating properties, ormay be epoxy-acrylic resins from the viewpoint of expectation of highcompressive strength.

The shape of the hollow resin particle is not particularly limited, aslong as a hollow portion is formed in the interior, and examples includea spherical shape, an ellipsoidal shape and an irregular shape. Amongthem, a spherical shape is preferable in terms of ease of production.

The interior of the hollow resin particles generally has one or two ormore hollow portions. The interior of the hollow resin particles may beporous as long as a hollow portion can be found. The interior of thehollow resin particles preferably has 5 or less hollow portions, morepreferably 3 or less hollow portions, still more preferably 2 or lesshollow portions, particularly preferably one hollow portion in order tomaintain good balance between a high void ratio of the hollow resinparticle and compressive strength of the hollow resin particle.

The average circularity of the hollow resin particles may be from 0.950to 0.995.

In the present disclosure, “circularity” is defined as a value obtainedby dividing the perimeter of a circle having the same area as theprojected area of a particle image, by the perimeter of the particleimage. Also in the present disclosure, the “average circularity” is usedas a simple method of quantitatively representing the shape of thehollow resin particles and is an indicator that shows the degree of thesurface roughness of the hollow resin particles. The average circularityis 1 when the hollow resin particles are perfectly spherical, and itgets smaller as the surface shape of the hollow resin particles becomesmore complex.

For the hollow resin particle of the present disclosure, the shellthickness may be from 0.01 μm to 1.0 μm, may be from 0.02 μm to 0.95 μm,and may be from 0.05 μm to 0.90 μm.

When the shell thickness is 0.01 μm or more, the hollow resin particlescan keep such a higher compressive strength that allows the particles tomaintain the shape thereof. When the shell thickness is 1.0 μm or less,the hollow portion with a larger volume can be ensured in the interiorof the hollow resin particle.

The method for measuring the shell thickness of the hollow resinparticle is as follows. First, 20 hollow resin particles are selected asmeasurement objects. SEM observation of the cross sections of the hollowresin particles is performed. Next, from the thus-obtained SEM images ofthe cross sections of the particles, the thicknesses of the shells ofthe 20 hollow resin particles are measured. The average of thethicknesses is determined as the shell thickness of the hollow resinparticle.

An example of an image of the shape of the hollow resin particle is abag that comprises a thin covering film and is swollen with gas, and across-sectional view of the bag is like a hollow resin particle 100 inFIG. 1 described later. In this example, one thin covering film isdisposed on the outside, and the interior is filled with gas.

The shape of the hollow resin particle can be determined by performingSEM and TEM, for example. Further, the shape of the interior of thehollow resin particle can be determined by cutting the particle intoround slices by a known method and then performing SEM and TEM, forexample.

[Method for Producing Hollow Resin Particles]

The method for producing the hollow resin particles is not particularlylimited, as long as the hollow resin particles that satisfy at least theabove-mentioned void ratio, can be produced by the method. Hereinbelow,an embodiment of the method for producing the hollow resin particles isdescribed, but the method for producing the hollow resin particles ofthe present disclosure is not limited to the following embodiment.

An embodiment of the method for producing the hollow resin particlesincludes:

a step comprising preparing a mixture liquid comprising anon-crosslinkable monomer, a crosslinkable monomer, an oil-solublepolymerization initiator, a hydrocarbon solvent, a suspension stabilizerand an aqueous medium (mixture liquid preparation step);

a step comprising carrying out a suspension treatment of the mixtureliquid described above to prepare a suspension in which monomer dropletscontaining the hydrocarbon solvent are dispersed in the aqueous medium(suspension preparation step);

a step comprising subjecting the suspension described above topolymerization reaction to prepare a precursor composition containing ahollow resin particle precursor including the hydrocarbon solvent(polymerization step);

a step comprising performing solid-liquid separation of the precursorcomposition described above to obtain a hollow resin particle precursor(solid-liquid separation step); and a step comprising removing thehydrocarbon solvent included in the hollow resin particle precursor toobtain a hollow resin particle (solvent removal step).

In the present disclosure, the “hollow resin particle precursor” means aparticle of which the hollow portion is filled with water or a mixtureof water and gas, or filled with an aqueous medium or a mixture of anaqueous medium and gas. In the present disclosure, the “precursorcomposition” means a composition containing a hollow resin particleprecursor.

The disclosed embodiment includes, as described above, (1) a mixtureliquid preparation step, (2) a suspension preparation step, (3) apolymerization step, (4) a solid-liquid separation step, and (5) asolvent removal step. The steps of the disclosed embodiment are notlimited to these five steps.

FIG. 1 is a schematic diagram showing the disclosed embodiment. Thediagrams (1) to (5) in FIG. 1 correspond to the steps (1) to (5)described above, respectively. The white arrow between the diagrams isone for indicating the order of the steps. FIG. 1 is only schematicdiagrams for description, and the method for producing the hollow resinparticles of the present disclosure is not limited to the method shownin FIG. 1. Further, the structures, dimensions, and shapes of materialsused for the method for producing the hollow resin particles of thepresent disclosure is not limited to the structures, dimensions, orshapes of the various materials in FIG. 1.

The diagram (1) of FIG. 1 is a schematic diagram showing an embodimentof a mixture liquid in the mixture liquid preparation step. As shown inthe diagram, the mixture liquid contains an aqueous medium 1 and a lowpolarity material 2 dispersed in the aqueous medium 1. Here, the lowpolarity material 2 means a material that has low polarity and is notlikely to mix with the aqueous medium 1, such as a monovinyl monomer anda hydrocarbon solvent.

The diagram (2) of FIG. 1 is a schematic diagram showing an embodimentof a suspension in the suspension preparation step. The suspensioncontains the aqueous medium 1 and a micelle 10 (monomer droplets)dispersed in the aqueous medium 1. The micelle 10 is formed bysurrounding the periphery of an oil-soluble monomer composition 4(containing, for example, an oil-soluble polymerization initiator 5)with a surfactant 3.

The diagram (3) of FIG. 1 is a schematic diagram showing an embodimentof a precursor composition after the polymerization step. The precursorcomposition contains the aqueous medium 1 and a hollow resin particleprecursor 20 dispersed in the aqueous medium 1. The hollow resinparticle precursor 20 is formed by polymerization of a monovinyl monomeretc. in the micelle 10, and includes the hydrocarbon solvent 7 in theinterior of the shell 6.

The diagram (4) of FIG. 1 is a schematic diagram showing an embodimentof a hollow resin particle precursor after the solid-liquid separationstep. The diagram (4) shows a state where an aqueous medium 1 isseparated from the state of the diagram (3).

The diagram (5) of FIG. 1 is a schematic diagram showing an embodimentof the hollow resin particle after the solvent removal step. The diagram(5) of FIG. 1 shows a state where a hydrocarbon solvent 7 is removedfrom the state of the diagram (4) of FIG. 1. As a result, a hollow resinparticle 100 having a hollow portion 8 in the interior of the shell 6 isobtained.

Hereinbelow, the five steps mentioned above and other steps aredescribed in order.

(1) Mixture Liquid Preparation Step

The present step is a step comprising preparing a mixture liquidcontaining (A) a non-crosslinkable monomer, (B) a crosslinkable monomer,(C) an oil-soluble polymerization initiator, (E) a hydrocarbon solvent,(F) a suspension stabilizer, and an aqueous medium.

Among them, (A) the non-crosslinkable monomer and (B) the crosslinkablemonomer are as described above in [Hollow resin particle]. Otherpolymerizable monomers may be contained in the mixture liquid, inaddition to (A) the non-crosslinkable monomer and (B) the crosslinkablemonomer, which are described above in

[Hollow Resin Particle]. (C) Oil-Soluble Polymerization Initiator

In the present disclosure, not an emulsion polymerization method using awater-soluble polymerization initiator but a suspension polymerizationmethod using an oil-soluble polymerization initiator is employed. Anadvantage of employing the suspension polymerization method will bedescribed in detail in “(2) Suspension preparation step”.

The oil-soluble polymerization initiator is not particularly limited, aslong as it is a lipophilic one having a solubility in water of 0.2% bymass or less. Examples of the oil-soluble polymerization initiatorinclude benzoyl peroxide, lauroyl peroxide, t-butyl peroxide2-ethylhexanoate, 2,2′-azobis(2,4-dimethylvaleronitrile), andazobis(isobutyronitrile).

With respect to 100 parts by mass of the total mass of (A) thenon-crosslinkable monomer and (B) the crosslinkable monomer, the contentof (C) the oil-soluble polymerization initiator is preferably from 0.1part by mass to 10 parts by mass, more preferably from 0.5 part by massto 7 parts by mass, and still more preferably from 1 part by mass to 5parts by mass. When the content of (C) the oil-soluble polymerizationinitiator is 0.1 part by mass or more, the polymerization reaction islikely to progress sufficiently. When the content of (C) the oil-solublepolymerization initiator is 10 parts by mass or less, the oil-solublepolymerization initiator is not likely to be left after the end ofpolymerization reaction, so that an unexpected side reaction is notlikely to progress.

(D) Hydrocarbon Solvent

The hydrocarbon solvent in the present disclosure has the function offorming a hollow portion in the interior of the particle.

In the suspension preparation step described later, a suspension inwhich monomer droplets containing a hydrocarbon solvent are dispersed inan aqueous medium is obtained. In the suspension preparation step, phaseseparation occurs in the monomer droplets; as a result, the hydrocarbonsolvent with low polarity is likely to collect in the interior of themonomer droplets. In the end, in the monomer droplets, the hydrocarbonsolvent is distributed in the interior and other materials than thehydrocarbon solvent are distributed at the periphery, in accordance withthe respective polarities.

Then, in the polymerization step described later, a precursorcomposition containing a hollow resin particle precursor including thehydrocarbon solvent is obtained. That is, the hydrocarbon solvent iscollected in the interior of the particle, so that a hollow portion madeof the hydrocarbon solvent is formed in the interior of the obtainedpolymer particle (hollow resin particle precursor).

The type of the hydrocarbon solvent is not particularly limited.Examples of the hydrocarbon solvent include solvents with relativelyhigh volatility, such as benzene, toluene, xylene, butane, pentane,hexane, heptane and cyclohexane.

The relative permittivity at 20° C. of the hydrocarbon solvent used inthe present disclosure is preferably 3 or less. The relativepermittivity is an index indicating the level of the polarity of thecompound. In the case where the relative permittivity of the hydrocarbonsolvent is 3 or less, which is sufficiently small, it is presumed thatphase separation progresses rapidly in the monomer droplets and a hollowis easily formed.

Examples of solvents having a relative permittivity at 20° C. of 3 orless are as follows. The inside of the parentheses is the value ofrelative permittivity.

Heptane (1.9), cyclohexane (2.0), benzene (2.3) and toluene (2.4).

For the relative permittivity at 20° C., values written in knownliteratures (for example, the Chemical Society of Japan, as editor,“Kagaku Binran, Kiso Hen, Kaitei 4 Ban”, pp. 11-498 to 11-503, publishedby Maruzen Publishing Co., Ltd. on Sep. 30, 1993) and other technicalinformation may be used as reference. Examples of the method ofmeasuring the relative permittivity at 20° C. include a relativepermittivity test that is in conformity with 23 of JIS C 2101:1999 andis performed with the measuring temperature set to 20° C.

The hydrocarbon solvent used in the present disclosure may be ahydrocarbon compound having 5 to 7 carbon atoms. A hydrocarbon compoundhaving 5 to 7 carbon atoms is easily included into a hollow resinparticle precursor during the polymerization step, and furthermore canbe easily removed from the interior of the hollow resin particleprecursor during the solvent removal step. The hydrocarbon solvent ispreferably a hydrocarbon compound having 6 carbon atoms.

With respect to 100 parts by mass of the total mass of (A) thenon-crosslinkable monomer and (B) the crosslinkable monomer, the contentof (D) the hydrocarbon solvent is preferably from 70 parts by mass to900 parts by mass, more preferably from 150 parts by mass to 700 partsby mass, and still more preferably from 200 parts by mass to 500 partsby mass. When the content of (D) the hydrocarbon solvent is 70 parts bymass or more, the void ratio of the obtained hollow resin particle islarge. When the content of (D) the hydrocarbon solvent is 900 parts bymass or less, the obtained hollow resin particle is likely to beexcellent in mechanical characteristics, and not likely to cause afailure of maintaining the hollow.

(E) Suspension Stabilizer

The suspension stabilizer is an agent that stabilizes a suspension statein a suspension in a suspension polymerization method described later.

The suspension stabilizer may contain at least any one of a surfactantand a material other than the surfactant. The surfactant is a materialthat forms a micelle including a non-crosslinkable monomer, acrosslinkable monomer, an oil-soluble polymerization initiator, anoil-soluble polymerization initiator and a hydrocarbon solvent, in thesuspension polymerization method described later.

As the surfactant, any of cationic surfactants, anionic surfactants, andnonionic surfactants may be used, and they may be used in combination.Among them, at least any one of anionic surfactants and nonionicsurfactants is preferable, and anionic surfactants are more preferable.

Examples of the anionic surfactant include sodium dodecylbenzensulfonate, sodium lauryl sulfate, dialkyl sodium sulfosuccinate andformalin condensate salt of naphthalene sulfonate.

Examples of the nonionic surfactant include polyoxyethylene alkyl ether,polyoxyethylene alkyl ester and polyoxyethylene sorbitan alkyl ester.

Examples of the cationic surfactant include didecyl dimethyl ammoniumchloride and stearyl trimethyl ammonium chloride.

Examples of the material other than the surfactant contained in thesuspension stabilizer, include a hardly-soluble inorganic compound suchas sulfate (e.g., barium sulfate and calcium sulfate), carbonate (e.g.,barium carbonate, calcium carbonate and magnesium carbonate), phosphate(e.g., calcium phosphate), metal oxide (e.g., aluminum oxide andtitanium oxide) and metal hydroxide (e.g., aluminum hydroxide, magnesiumhydroxide and iron(II)hydroxide) and a water-soluble polymer such aspolyvinyl alcohol, methyl cellulose and gelatin.

The material other than the surfactant is preferably a hardly-solubleinorganic compound, more preferably at least one of phosphate and metalhydroxide, and particularly preferably hardly water-soluble metalhydroxide colloid.

As the suspension stabilizer, one or more kinds of suspensionstabilizers may be used.

With respect to 100 parts by mass of the total mass of (A) thenon-crosslinkable monomer, (B) the crosslinkable monomer, (C) theoil-soluble polymerization initiator and (D) the hydrocarbon solvent,the content of (E) the suspension stabilizer is preferably from 0.1 partby mass to 5 parts by mass, more preferably from 0.2 part by mass to 2parts by mass, and still more preferably from 0.3 part by mass to 1 partby mass. When the content of (E) the suspension stabilizer is 0.1 partby mass or more, micelles are easily formed in an aqueous medium. Whenthe content of (E) the suspension stabilizer is 5 parts by mass or less,a reduction in productivity by increasing in blowing in the step ofremoving the hydrocarbon solvent is not likely to occur.

(F) Others

In the present disclosure, the aqueous medium means one of water, ahydrophilic solvent and a mixture of water and a hydrophilic solvent.

The hydrophilic solvent in the present disclosure is not particularlylimited, as long as it is one that mixes with water sufficiently anddoes not develop phase separation. Examples of the hydrophilic solventinclude alcohols such as methanol and ethanol; tetrahydrofuran (THF);and dimethyl sulfoxide (DMSO).

Among the aqueous media, water is preferably used in terms of its highpolarity. When a mixture of water and a hydrophilic solvent is used, itis important that the polarity of the entire mixture is not too low fromthe viewpoint of forming monomer droplets. For example, the mixing ratio(mass ratio) between water and the hydrophilic solvent may be set towater:hydrophilic solvent=99:1 to 50:50.

The mixture liquid prepared in the present step is a composition in astate where the materials (A) to (E) mentioned above and an aqueousmedia are simply mixed and, for example, stirred as appropriate. In themixture liquid, oil phases containing the materials (A) to (D) mentionedabove are dispersed in an aqueous medium, each with a size of a particlediameter of approximately several millimeters. The dispersion state ofthese materials in the mixture liquid can be observed with the nakedeye, depending on the types of the materials.

In the present step, an oil phase which contains (A) thenon-crosslinkable monomer, (B) the crosslinkable monomer, (C) theoil-soluble polymerization initiator and (D) the hydrocarbon solvent andin which the content of (B) the crosslinkable monomer is from 30 partsby mass to 100 parts by mass with respect to 100 parts by mass of thetotal mass of (A) the non-crosslinkable monomer and (B) thecrosslinkable monomer, may be mixed with an aqueous phase containing (E)the suspension stabilizer and the aqueous medium to prepare a mixtureliquid. Particles of which the compositions are uniform can be producedby thus mixing the oil phase and the aqueous phase.

(2) Suspension Preparation Step

The present step is a step comprising carrying out a suspensiontreatment of the mixture liquid described above to prepare a suspensionin which monomer droplets containing the hydrocarbon solvent aredispersed in the aqueous medium.

In the suspension prepared in the present step, monomer droplets eachcontaining the materials (A) to (D) mentioned above and having a volumeaverage particle diameter of approximately from 1.0 μm to 20 μm aredispersed uniformly in the aqueous medium. Such monomer droplets aredifficult to be observed with the naked eye, and can be observed with,for example, known observation equipment such as an optical microscope.

As described above, not an emulsion polymerization method but asuspension polymerization method is employed in the present disclosure.Hereinbelow, an advantage of using a suspension polymerization methodand an oil-soluble polymerization initiator is described with contrastto an emulsion polymerization method.

FIG. 2 is a schematic diagram showing an embodiment of a suspension inthe suspension preparation step. A micelle 10 in FIG. 2 schematicallyshows a cross section thereof. FIG. 2 is only a schematic diagram, andthe suspension in the present disclosure is not necessarily limited tothat shown in FIG. 2. A part of FIG. 2 corresponds to the diagram (2) ofFIG. 1 described above.

FIG. 2 shows a situation where micelles 10 and pieces of monomers 4 a(including the monovinyl monomer and the crosslinkable monomer) that aredispersed in an aqueous medium, are dispersed in an aqueous medium 1.The micelle 10 is formed by a surfactant 3 surrounding the periphery ofan oil-soluble monomer composition 4. The monomer composition 4 containsan oil-soluble polymerization initiator 5, monomers (including amonovinyl monomer and a crosslinkable monomer) and a hydrocarbon solvent(none of them is illustrated).

As shown in FIG. 2, in the suspension preparation step, a minute oildroplet that is a micelle 10 which contains the monomer composition 4 inthe interior is formed in advance, and then polymerization initiatingradicals are generated in the minute oil droplet from the oil-solublepolymerization initiator 5. Therefore, a hollow resin particle precursorwith a target particle diameter can be produced without excessivelygrowing the minute oil droplet.

FIG. 3 is a schematic diagram showing a dispersion for emulsionpolymerization. A micelle 60 in FIG. 3 schematically shows a crosssection thereof.

FIG. 3 shows a situation where micelles 60, pieces of a micelleprecursor 60 a, pieces of a monomer 53 a dissolved out in a solvent, andpieces of a water-soluble polymerization initiator 54 are dispersed inan aqueous medium 51. The micelle 60 is formed by a surfactant 52surrounding the periphery of an oil-soluble monomer composition 53. Themonomer composition 53 contains, for example, a monomer serving as asource material of a polymer, but does not contain a polymerizationinitiator.

On the other hand, the micelle precursor 60 a is an aggregate of piecesof the surfactant 52, but does not contain a sufficient amount of themonomer composition 53 in the interior. The micelle precursor 60 a, forexample, incorporates pieces of the monomer 53 a dissolved out in thesolvent into the interior of the micelle precursor, and procures a partof the monomer composition 53 from other micelles 60; thereby, growsinto the micelle 60.

The water-soluble polymerization initiator 54 enters the interiors ofthe micelle 60 and the micelle precursor 60 a, and promotes the growthof oil droplets in the interiors of them while being diffused in theaqueous medium 51. Therefore, in the emulsion polymerization method,although each micelle 60 is monodispersed in the aqueous medium 51, itis predicted that the particle diameter of the micelle 60 will grow upto several hundred nm.

Further, as can be seen by comparing suspension polymerization (FIG. 2)and emulsion polymerization (FIG. 3), suspension polymerization (FIG. 2)does not provide an opportunity for the oil-soluble polymerizationinitiator 5 to come into contact with the monomer 4 a dispersed in theaqueous medium 1. Thus, the generation of surplus polymer particles inaddition to target hollow resin particles can be prevented by using anoil-soluble polymerization initiator.

A typical example of the suspension preparation step is shown below.

A mixture liquid containing the materials (A) to (E) mentioned above issubjected to the suspension treatment to form monomer droplets. Themethod of forming monomer droplets is not particularly limited; forexample, the formation is performed using an apparatus capable ofperforming strong stirring, such as an (in-line type) emulsifyingdisperser (manufactured by Pacific Machinery & Engineering Co., Ltd.;product name: MILDER) or a high-speed emulsifying disperser(manufactured by PRIMIX Corporation; product name: T.K. HOMOMIXER MARKII Type).

As described above, in the present step, since phase separation occursin the monomer droplet, the hydrocarbon solvent with low polarity islikely to collect in the interior of the monomer droplet. As a result,in the obtained monomer droplet, the hydrocarbon solvent is distributedin the interior, and other materials than the hydrocarbon solvent aredistributed at the periphery.

A modified example of the suspension preparation step is shown below.

First, an oil phase containing the materials (A) to (D) mentioned aboveand an aqueous phase containing the material (E) and an aqueous mediumare prepared, respectively. The oil phase is prepared preferably as thecontent of (B) the crosslinkable monomer is from 30 parts by mass to 100parts by mass, with respect to 100 parts by mass of the total mass of(A) the non-crosslinkable monomer and (B) the crosslinkable monomer.

Next, a suspension is prepared by a membrane emulsification method. Themembrane emulsification method is a method for obtaining, by extruding adispersion phase solution into a continuous phase through the pores of aporous membrane, a suspension in which minute droplets of the dispersionphase are dispersed in the continuous phase. The dispersion phase meansa liquid phase dispersed in the form of minute droplets, and thecontinuous phase means a liquid phase surrounding the periphery of thedispersion phase droplets. In the present disclosure, both a directmembrane emulsification method and a membrane emulsification methodinvolving preliminary emulsification, etc., may be employed, as long asthey are membrane emulsification methods in which the oil phase is madeinto the dispersion phase and the aqueous phase is made into thecontinuous phase.

In the membrane emulsification method, a membrane emulsification system(such as MN-20 manufactured by SPG Technology Co., Ltd.) and a membranehaving a specific pore diameter are used. As the porous membrane usablein the membrane emulsification method, examples include, but are notlimited to, an inorganic porous membrane such as a shirasu porous glassmembrane (an SPG membrane) and an organic porous membrane such as a PTFE(polytetrafluoroethylene resin) membrane.

The pore diameter of the porous membrane used in the membraneemulsification method defines the diameter of the obtained minutedroplets. Depending on the components in the dispersion phase, since thediameter of the minute droplets has an influence on the number averageparticle diameter of the obtained hollow resin particles, the selectionof the pore diameter of the porous membrane is important. For example,in the case of using a shirasu porous glass membrane (an SPG membrane),the pore diameter of the membrane is preferably selected from 0.1 μm to5.0 μm.

In the suspension preparation step using such a membrane emulsificationmethod, the suspension is prepared by performing the membraneemulsification in which the oil phase and the aqueous phase are madeinto the dispersion phase and the continuous phase, respectively, usingthe above-mentioned membrane emulsification system and theabove-mentioned porous membrane.

The suspension preparation step of the present embodiment is not limitedto the typical example and the modified example mentioned above.

(3) Polymerization Step

The present step is a step comprising subjecting the suspensiondescribed above to polymerization reaction to prepare a precursorcomposition containing a hollow resin particle precursor including thehydrocarbon solvent. Here, a hollow resin particle precursor is aparticle formed mainly by copolymerization of the at least onenon-crosslinkable monomer selected from the group consisting of themonovinyl monomer and the hydrophilic monomer, and the crosslinkablemonomer described above.

The polymerization system is not particularly limited; for example, abatch system, a semicontinuous system and a continuous system may beemployed. The polymerization temperature is preferably from 40° C. to80° C., and more preferably from 50° C. to 70° C. The polymerizationreaction time is preferably from 1 hour to 20 hours, and more preferablyfrom 2 hours to 15 hours.

Since a monomer droplet including the hydrocarbon solvent in theinterior is used, as described above, the hollow consisting of thehydrocarbon solvent is formed in the interior of the hollow resinparticle precursor.

(4) Solid-Liquid Separation Step

The present step is a step comprising performing solid-liquid separationof the precursor composition described above to obtain a hollow resinparticle precursor.

In the case where a hydrocarbon solvent included in a hollow resinparticle precursor is removed in a slurry containing an aqueous medium,there is a problem that the obtained hollow resin particle collapsesunless the same volume of water as the hydrocarbon solvent released fromthe interior of the hollow resin particle precursor, enters the interiorof the particle.

A possible method to prevent the problem is a method in which the pH ofthe slurry is set to 7 or more to alkali-swell the shell of theparticle, and then the hydrocarbon solvent is removed. In this case,since the shell of the particle acquires flexibility, replacement of thehydrocarbon solvent in the interior of the particle with waterprogresses rapidly, and a particle including water is obtained.

The method of performing solid-liquid separation of the precursorcomposition is not particularly limited, as long as it is a method thatseparates the solid components containing the hollow resin particleprecursor and the liquid components containing the aqueous mediumwithout removing the hydrocarbon solvent included in the hollow resinparticle precursor, and known methods may be used. Examples of themethod of solid-liquid separation include a centrifugation method, afiltration method, and still-standing separation; among them, acentrifugation method or a filtration method may be employed, and fromthe viewpoint of simplicity of the operation, a centrifugation methodmay be employed.

An optional step such as a preliminary drying step may be performed at atime after the solid-liquid separation step and before performing thesolvent removal step described later. Examples of the preliminary dryingstep include a step comprising performing preliminary drying on thesolid components obtained after the solid-liquid separation step, with adrying apparatus such as a dryer and a drying appliance such as a handdryer.

(5) Solvent removal step

The present step is a step comprising removing the hydrocarbon solventincluded in the hollow resin particle precursor to obtain a hollow resinparticle.

The hydrocarbon solvent included in the hollow resin particle precursormay be removed in a gaseous atmosphere, or it may be removed in liquid.

In a strict sense, the term “in a gaseous atmosphere” in the presentstep means “in an environment where no liquid components exist in theoutside of the hollow resin particle precursor”, and it means “in anenvironment where only a very small amount of liquid components at alevel that does not influence the removal of the hydrocarbon solventexist in the outside of the hollow resin particle precursor”. The term“in a gaseous atmosphere” can be reworded as a state where the hollowresin particle precursor does not exist in a slurry, or can be rewordedas a state where the hollow resin particle precursor exists in a drypowder.

The method of removing the hydrocarbon solvent in the hollow resinparticle precursor is not particularly limited, and known methods may beemployed. Examples of the method include the reduced pressure dryingmethod, the heat drying method, and the flash drying method, and use ofthese methods in combination.

In particular, in the case where the heat drying method is used, theheating temperature needs to be set to more than or equal to the boilingpoint of the hydrocarbon solvent and less than or equal to the highesttemperature at which the shell structure of the hollow resin particledoes not collapse. Therefore, depending on the composition of the shellof the hollow resin particle precursor and the type of the hydrocarbonsolvent, for example, the heating temperature may be from 50° C. to 250°C., may be from 100° C. to 240° C., and may be from 150° C. to 220° C.The heating time may be from 1 hour to 24 hours, preferably from 2 hoursto 15 hours, and more preferably from 3 hours to 10 hours.

The hydrocarbon solvent in the interior of the hollow resin particleprecursor is replaced with gas in the outside by drying operation in agaseous atmosphere; as a result, a hollow resin particle in which thegas occupies the hollow portion is obtained.

The drying atmosphere is not particularly limited. Examples of thedrying atmosphere include air, oxygen, nitrogen, argon and vacuum.Further, by filling the interior of the hollow resin particle with gasonce and then performing reduced pressure drying, a hollow resinparticle of which the interior is evacuated is also obtained.

(6) Others

A possible example of a step other than the steps (1) to (5) mentionedabove, is a step in which the gas in the interior of the hollow resinparticle is replaced with another gas or liquid. By such replacement,the environment of the interior of the hollow resin particle can bechanged, molecules can be selectively confined in the interior of thehollow resin particle, or the chemical structure of the interior of thehollow resin particle can be modified in accordance with the intendedapplication thereof.

[Resin Composition Production Method]

As the method for producing the resin composition of the presentdisclosure, a method that is generally used for resin compositionproduction, may be employed. The resin composition can be produced byuniformly integrating the components with, for example, a melt-kneadersuch as a single screw extruder, a twin screw extruder, a banbury mixer,a heating roller and various kinds of kneaders.

By using the resin composition of the present disclosure, the moldedproduct having the specific void ratio can be stably obtained through amolding process that is carried out in a heat-pressing condition,without causing the hollow resin particles in the resin composition tocollapse. Accordingly, the resin composition of the present disclosurecan be suitably used in a molding method that is carried out in aheat-pressing condition, such as injection molding and compressionmolding.

From the resin composition of the present disclosure, a lightweightmolded product can be obtained by any other known molding method such asextrusion molding, blow molding, calendering, inflation molding, blowmolding, stretch molding and solution casting.

By the above-mentioned molding method, the resin composition of thepresent disclosure can be formed into a molded product in any shape,such as various kinds of three-dimensional shapes, a sheet shape, a filmshape and a tube shape.

The resin composition of the present disclosure can be used as a rawmaterial for various kinds of industrial products, industrial parts,etc.

More specifically, the resin composition of the present disclosure canbe used as a raw material for the following: automobile parts such as aweather strip, an upholstery material, an airbag cover, a packing, andvarious kinds of sealing members; home appliance parts such as a ricecooker packing, a washing machine drain hose and a power code; medicalproducts such as a syringe gasket and a medical tube; sporting goodsapplications such as a sports shoe sole and a ski plate; and civilengineering and building applications such as a waterproof sheet, ahose, a tube, a wire coating material and a cushioning material.

As the applications of the molded product of the present disclosure,examples include, but are not limited to, parts used in various kinds offields such as the automotive field, the electrical and electronicfield, the architecture field and the aerospace field; food containers;light reflective materials; heat insulation materials; sound insulationmaterials; and low dielectric materials.

EXAMPLES

Hereinafter, unless otherwise noted, “part” means “part by mass”.

1. Production of Hollow Resin Particles Production Example 1 (1) MixtureLiquid Preparation Step

First, materials (a1) to (d1) mentioned below were mixed to obtain amixture (an oil phase).

(a1) Methacrylic acid: 40 parts

(b1) Ethylene glycol dimethacrylate: 60 parts

(c1) 2,2′-Azobis(2,4-dimethylvaleronitrile) (an oil-solublepolymerization initiator, manufactured by Wako Pure Chemical Industries,Ltd., product name: V-65): 3 parts

(d1) Cyclohexane: 150 parts

Next, 4.0 parts of (e) a surfactant was added to 800 parts ofion-exchanged water to obtain a mixture (an aqueous phase).

The aqueous phase and the oil phase were mixed, and thus a mixtureliquid was prepared.

(2) Suspension Preparation Step

The mixture liquid mentioned above was stirred with an in-line typeemulsifying disperser to be suspended, and a suspension in which monomerdroplets including cyclohexane were dispersed in water was prepared.

(3) Polymerization Step

The suspension mentioned above was stirred in a nitrogen atmosphere at65° C. for 4 hours, and polymerization reaction was performed. By thispolymerization reaction, a precursor composition containing a hollowresin particle precursor including cyclohexane was prepared.

(4) Solid-Liquid Separation Step

The obtained precursor composition was filtered to obtain solidcomponents. The obtained solid components were dried with a dryer at atemperature of 40° C., and a hollow resin particle precursor includingcyclohexane was obtained.

(5) Solvent Removal Step

The hollow resin particle precursor was subjected to heating treatmentwith a vacuum dryer at 200° C. for 6 hours in a vacuum condition, andthereby particles of Production Example 1 were obtained. From thescanning electron microscopy result and void ratio value of theparticles, the obtained particles were confirmed to be hollow resinparticles being in a spherical shape and having a hollow portion.

Production Examples 2 to 3

The particles of Production Examples 2 and 3 were obtained by a similarproduction method to Production Example 1, except that the materials andthe addition amounts shown in Table 1 were employed in “(1) Mixtureliquid preparation step” of Production Example 1. From the scanningelectron microscopy result and void ratio value of the particles, theobtained particles of Production Examples 2 and 3 were confirmed to behollow resin particles being in a spherical shape and having a hollowportion.

Production Example 4

The particles of Production Example 4 were obtained by a similarproduction method to Production Example 1, except the following: thematerials and addition amounts shown in Table 1 were employed in “(1)Mixture liquid preparation step” of Production Example 1; the aqueousphase and the oil phase were supplied to the next “(2) Suspensionpreparation step” without mixing them; and in “(2) Suspensionpreparation step” of Production Example 1, a suspension was prepared by,instead of a suspension method using an in-line type emulsifyingdisperser, performing membrane emulsification in which the oil phase andthe aqueous phase were made into the dispersion phase and the continuousphase, respectively, using a membrane emulsification system and ashirasu porous glass membrane having a pore diameter of 5 μm. From thescanning electron microscopy result and void ratio value of theparticles, the obtained particles were confirmed to be hollow resinparticles being in a spherical shape and having a hollow portion.

Production Examples 5 to 6

The particles of Production Examples 5 and 6 were obtained by a similarproduction method to Production Example 1, except the following: thematerials and addition amounts shown in Table 1 were employed in “(1)Mixture liquid preparation step” of Production Example 1. From thescanning electron microscopy result and void ratio value of theparticles, the obtained particles of Production Examples 5 and 6 wereconfirmed to be hollow resin particles being in a spherical shape andhaving a hollow portion.

Production Example 7

The particles of Production Example 7 were obtained by a similarproduction method to Production Example 1, except the following: thematerials and addition amounts shown in Table 1 were employed in “(1)Mixture liquid preparation step” of Production Example 1; the aqueousphase and the oil phase were supplied to the next “(2) Suspensionpreparation step” without mixing them; and in “(2) Suspensionpreparation step” of Production Example 1, a suspension was prepared by,instead of a suspension method using an in-line type emulsifyingdisperser, performing membrane emulsification in which the oil phase andthe aqueous phase were made into the dispersion phase and the continuousphase, respectively, using a membrane emulsification system and ashirasu porous glass membrane having a pore diameter of 10 μm. From thescanning electron microscopy result and void ratio value of theparticles, the obtained particles were confirmed to be hollow resinparticles being in a spherical shape and having a hollow portion.

Production Example 8

First, materials (a2), (α1), (α2), (c2) and (d2) mentioned below weremixed to obtain a mixture (an oil phase).

(a2) Methacrylic acid: 45 parts

(α1) Acrylonitrile: 30 parts

(α2) Methacrylonitrile: 25 parts

(c2) Azobis(isobutyronitrile): 5 parts

(d2) Isopentane: 30 parts

Next, 200 parts of (y) a colloidal silica dispersion (the averageparticle diameter: 5 nm; the effective concentration of colloidalsilica: 20% by mass) was added to 600 parts of ion-exchanged water toobtain a mixture (an aqueous phase).

The aqueous phase and the oil phase were mixed, and thus a mixtureliquid was prepared.

The mixture liquid mentioned above was stirred with a disperser andsuspended to obtain a suspension. The obtained suspension was stirred ata temperature condition of 60° C. for 10 hours, and a polymerizationreaction was performed.

The suspension after the polymerization reaction was filtered to obtainsolid components. The obtained solid components were dried with a dryerat 40° C. to obtain the particles of Production Example 8, which arethermally expandable microcapsules.

Production Example 9

The particles of Production Example 9 were obtained by a similarproduction method to Production Example 1, except that the materials andthe addition amounts shown in Table 1 were employed in “(1) Mixtureliquid preparation step” of Production Example 1. From the scanningelectron microscopy result and void ratio value of the particles, theobtained particles were confirmed to be hollow resin particles being ina spherical shape and having a hollow portion.

2. Measurement and Evaluation of Particles

The following measurement and evaluation were performed on the hollowresin particles of Production Examples 1 to 9 (hereinafter, the hollowresin particles may be simply referred to as “particles”). Details areas follows.

(1) Measurement of Volume Average Particle Diameter of Particles

The particle diameter of each particle was measured using a laserdiffraction particle size distribution measuring instrument (productname: SALD-2000, manufactured by: Shimadzu Corporation). The volumeaverage of them were calculated, and the obtained value was taken as thevolume average particle diameter of the particles.

(2) Measurement of Density of Particle and Calculation of Void Ratio A.Measurement of Apparent Density of Particle

First, approximately 30 cm³ of the particles were introduced into ameasuring flask with a volume of 100 cm³, and the mass of the introducedparticles was precisely weighed. Next, the measuring flask in which theparticles were introduced was precisely filled with isopropanol up tothe marked line while care was taken so that air bubbles did not get in.The mass of the isopropanol added to the measuring flask was preciselyweighed, and the apparent density D₁ (g/cm³) of the particle wascalculated on the basis of Formula (I) mentioned below.

Apparent density D ₁=[Mass of the hollow resin particles]/(100−[Mass ofthe isopropanol]/[Specific gravity of the isopropanol at the measuringtemperature])  Formula (I)

B. Measurement of True Density of Particle

The particles were pulverized in advance; then, approximately 10 g ofpulverized pieces of the particles were introduced into a measuringflask with a volume of 100 cm³, and the mass of the introducedpulverized pieces was precisely weighed.

After that, similarly to the measurement of the apparent densitymentioned above, isopropanol was added to the measuring flask, the massof the isopropanol was precisely weighed, and the true density D₀(g/cm³) of the particle was calculated on the basis of Formula (II)mentioned below.

True density D ₀=[Mass of the pulverized pieces of the hollow resinparticles]/(100−[Mass of the isopropanol]/[Specific gravity of theisopropanol at the measuring temperature])  Formula (II)

C. Calculation of Void Ratio

On the basis of the following formula (0), the apparent density D₁ wasdivided by the true density D₀; the resultant was multiplied by 100; andthe value thus obtained was subtracted from 100, thereby calculating thevoid ratio of the particle.

Void ratio (%)=100−[Apparent density D ₁]/[True density D₀]×100  Formula (0)

(3) Measurement of Glass Transition Temperature (Tg) of Particles

The glass transition temperature was measured on the basis of JIS K6911using a differential scanning calorimeter (product name: DSC6220,manufactured by Seiko Instruments, Inc.) For the particles for whichglass transition was not observed in a temperature range of from 0° C.to 250° C., the glass transition temperature of the particles wasconsidered to be more than 250° C. and was not mentioned in Table 1.That is, it was revealed that the particles of Production Examples 1 to7 and 9 do not cause glass transition in a temperature range of from 0°C. to 250° C., and the glass transition temperature of the particles ismore than 250° C.

TABLE 1 Production Production Production Production Production Example 1Example 2 Example 3 Example 4 Example 5 Non- Methacrylic acid 40 15 3015 35 crosskinkable (parts) monomer Methyl — 25 20 — — methacrylate(parts) Butyl acrylate — 20 — — — (parts) Acrylonitrile (parts) — — — —— Methacrylonitrile — — — — — (parts) Crosskinkable Ethylene glycol 6040 — 85 65 monomer dimethacrylate (parts) Divinyl benzene — — 50 — —(parts) Oil-soluble polymerization initiator 3 3 3 3 3 (parts)Hydrocarbon Cyclohexane (parts) 150 80 100 300 600 solvent Isopentane(parts) — — — — — Suspension Magnesium — — — — — stabilizer hydroxidecolloid (pasts) Surfactant (parts) 4.0 3.0 1.0 3.0 2.7 Colloidal silica— — — — — dispersion (parts) Ion-exchanged water (parts) 800 800 800 800800 Volume average particle diameter Dv 2.8 3.8 4.6 15.4 2.3 (μm) Numberaverage particle diameter Dn 2.6 3.4 3.5 12.8 2.1 (μm) Particle sizedistribution Dv/Dn 1.08 1.12 1.31 1.20 1.10 Apparent density D₁ (g/cm³)0.36 0.55 0.48 0.20 0.12 True density D₀ (g/cm³) 1.20 1.20 1.19 1.191.19 Void ratio (%) 70 55 60 83 90 Tg (° C.) — — — — — ProductionProduction Production Production Example 6 Example 7 Example 8 Example 9Non- Methacrylic acid 15 20 45 — crosskinkable (parts) monomer Methyl 5545 — — methacrylate (parts) Butyl acrylate 15 10 — — (parts)Acrylonitrile (parts) — — 30 — Methacrylonitrile — — 25 — (parts)Crosskinkable Ethylene glycol 15 25 — 100 monomer dimethacrylate (parts)Divinyl benzene — — — — (parts) Oil-soluble polymerization initiator 3 35 3 (parts) Hydrocarbon Cyclohexane (parts) 45 80 — 187 solventIsopentane (parts) — — 30 — Suspension Magnesium — — — 8 stabilizerhydroxide colloid (pasts) Surfactant (parts) 0.8 3.0 — — Colloidalsilica — — 200 — dispersion (parts) Ion-exchanged water (parts) 800 800600 1500 Volume average particle diameter Dv 4.2 25.5 3.4 6.2 (μm)Number average particle diameter Dn 3.5 20.1 3.0 5.2 (μm) Particle sizedistribution Dv/Dn 1.20 1.27 1.13 1.19 Apparent density D₁ (g/cm³) 0.710.55 1.21 0.36 True density D₀ (g/cm³) 1.19 1.20 — 1.20 Void ratio (%)40 55 Unexpanded 70 Tg (° C.) — — 237 —

2. Production of Resin Composition Example 1

First, 80 parts of a polyolefin-based thermoplastic elastomer(“THERMORUN 3655B” manufactured by Mitsubishi Chemical Corporation) and20 parts of the hollow resin particles obtained in Production Example 1were mixed by a blender. Next, the mixture was kneaded by a biaxialkneader (product name: TEM-35B, manufactured by Toshiba Machine Co.,Ltd.) and extruded into a pellet, thereby obtaining the pellet of aresin composition (1).

The obtained pellet of the resin composition (₁) was dried by heating at80° C. for 6 hours and then molded with an injection molding device,thereby obtaining the molded product of Example 1, which had a size of80 mm×10 mm×thickness 4 mm.

The specific gravity of the molded product of Example 1, which wasobtained by the underwater replacement method in conformity with JIS K7112, was measured, and the weight reduction ratio, specific gravityincrease ratio and specific gravity variation of the molded product ofExample 1 were calculated.

In the present disclosure, the weight reduction ratio is the ratio ofweight reduction when the mass of the molded product formed by use ofthe resin consisting of only the thermoplastic elastomer, is determinedas the reference.

The weight reduction ratio was calculated by the following formula:

Weight reduction ratio (%)=100×(1−Specific gravity of the moldedproduct/Specific gravity of the thermoplastic elastomer)

In the present disclosure, when the specific gravity (i.e., thetheoretical specific gravity of the molded product) is calculated fromthe specific gravities and mass ratios of the thermoplastic elastomerand hollow resin particles, which are raw materials, and is determinedas the reference, the specific gravity increase ratio is the ratio ofincrease in the specific gravity of the molded product obtained byheat-pressing and molding the resin composition. The specific gravityincrease ratio is an index of the collapse resistance of the hollowresin particles. That is, the fact that the specific gravity of themolded product is equal to the theoretical specific gravity of themolded product (the specific gravity increase ratio: 0%) indicates thatthe hollow resin particles do not collapse in the kneading and moldingprocesses, and the hollow of the particles is maintained even after theprocesses are carried out on the particles.

The specific gravity increase ratio was calculated by the followingformula:

Specific gravity increase ratio (%)=100×(Specific gravity of the moldedproduct/Theoretical specific gravity of the molded product−1)

On the basis of the following formula and from the mass ratios andspecific gravities of the thermoplastic elastomer and hollow resinparticles, the theoretical specific gravity of the molded product wasobtained by adding the value obtained by multiplying the mass ratio (a)of the thermoplastic elastomer by the specific gravity of thethermoplastic elastomer and the value obtained by multiplying the massratio (1-a) of the hollow resin particles by the specific gravity of thehollow resin particles.

Theoretical specific gravity (g/cm³) of the molded product=(a)×[Specificgravity (g/cm³) of the thermoplastic elastomer]+(1−a)×[Specific gravity(g/cm³) of the hollow resin particles]

The specific gravity variation was obtained as follows. The gate sideand non-gate side of the molded product were each cut into a size of 10mm×10 mm×4 mm, and a difference in specific gravity was obtained. Thisprocess was carried out on 10 molded products, and the average wasdetermined as the specific gravity variation.

Examples 2 to 4

The resin compositions and molded products of Examples 2 to 4 wereobtained by a similar production method to Example 1, except that thematerials and addition amounts shown in Table 2 were employed. Thespecific gravities of the molded products of Examples 2 to 4, which wereobtained by the underwater replacement method in conformity with JIS K7112, were measured, and the weight reduction ratios, specific gravityincrease ratios and specific gravity variations of the molded productsof Examples 2 to 4 were calculated.

Example 5

The resin composition and molded product of Example 5 were obtained by asimilar production method to Example 1, except that the materials andaddition amounts shown in Table 2 were employed. In Example 5, apolyurethane-based thermoplastic elastomer (“MIRACTRAN E390”manufactured by Nippon Miractran Co., Ltd.) was used as thethermoplastic elastomer. The specific gravity of the molded product ofExample 5, which was obtained by the underwater replacement method inconformity with JIS K 7112, was measured, and the weight reductionratio, specific gravity increase ratio and specific gravity variation ofthe molded product of Example 5 were calculated.

Example 6

The resin composition and molded product of Example 6 were obtained by asimilar production method to Example 1, except that the materials andaddition amounts shown in Table 2 were employed. In Example 6, apolystyrene-based thermoplastic elastomer (“RABALON 7400B” manufacturedby Mitsubishi Chemical Corporation) was used as the thermoplasticelastomer. The specific gravity of the molded product of Example 6,which was obtained by the underwater replacement method in conformitywith JIS K 7112, was measured, and the weight reduction ratio, specificgravity increase ratio and specific gravity variation of the moldedproduct of Example 6 were calculated.

Example 7

The resin composition and molded product of Example 7 were obtained by asimilar production method to Example 1, except that the materials andaddition amounts shown in Table 2 were employed. The specific gravity ofthe molded product of Example 7, which was obtained by the underwaterreplacement method in conformity with JIS K 7112, were measured, and theweight reduction ratio, specific gravity increase ratio and specificgravity variation of the molded product of Example 7 were calculated.

Comparative Examples 1 to 3

The resin compositions and molded products of Comparative Examples 1 to3 were obtained by a similar production method to Example 1, except thatthe materials and addition amounts shown in Table 2 were employed. Thespecific gravities of the molded products of Comparative Examples 1 to3, which were obtained by the underwater replacement method inconformity with JIS K 7112, were measured, and the weight reductionratios, specific gravity increase ratios and specific gravity variationsof the molded products of Comparative Examples 1 to 3 were calculated.

Comparative Example 4

The resin composition and molded product of Comparative Example 4 wereobtained by a similar production method to Example 1, except that thematerials and addition amounts shown in Table 2 were employed. Thespecific gravity of the molded product of Comparative Example 4, whichwas obtained by the underwater replacement method in conformity with JISK 7112, was measured, and the weight reduction ratio, specific gravityincrease ratio and specific gravity variation of the molded product ofComparative Example 4 were calculated.

Comparative Example 5

The resin composition and molded product of Comparative Example 5 wereobtained by a similar production method to Example 1, except that glassballoons (“GLASS BUBBLES IM30K” manufactured by 3M) were used as thehollow resin particles, and the materials and addition amounts shown inTable 2 were employed. The specific gravity of the molded product ofComparative Example 5, which was obtained by the underwater replacementmethod in conformity with JIS K 7112, was measured, and the weightreduction ratio, specific gravity increase ratio and specific gravityvariation of the molded product of Comparative Example 5 werecalculated.

TABLE 2 Theoretical specific Specific Resin composition (parts) gravityof gravity of Specific Specific Hollow Hollow molded molded Weightgravity gravity Resin Thermoplastic resin Thermoplastic resin productproduct reduction increase variation composition elastomer particleselastomer particles (g/cm³) (g/cm³) ratio (%) ratio (%) (g/cm³) Example1 Polyolefin- Production 80 20 0.689 0.696 22 1 0.012 based Example 1Example 2 Polyolefin- Production 50 50 0.677 0.691 23 2 0.013 basedExample 2 Example 3 Polyolefin- Production 70 30 0.710 0.738 17 4 0.010based Example 3 Example 4 Polyolefin- Production 90 10 0.663 0.690 23 40.014 based Example 4 Example 5 Polyurethane- Production 90 10 0.9760.986 18 1 0.018 based Example 1 Example 6 Polystyrene- Production 80 200.846 0.880 10 4 0.015 based Example 2 Example 7 Polyolefin- Production80 20 0.689 0.693 22 1 0.010 based Example 9 Comparative Polyolefin-Production 95 5 0.675 0.878 2 30 0.015 Example 1 based Example 5Comparative Polyolefin- Production 50 50 0.791 0.890 0 13 0.013 Example2 based Example 6 Comparative Polyolefin- Production 90 10 0.726 0.856 418 0.034 Example 3 based Example 7 Comparative Polyolefin- Production 9010 — 0.653 27 — 0.053 Example 4 based Example 8 Comparative Polyolefin-Glass 70 30 0.779 0.877 2 13 0.010 Example 5 based balloons

For Examples 1 to 7, the weight reduction ratio is 10% or more and high,and the specific gravity increase ratio is 4% or less and small. Theresults indicate that the hollow structure of the hollow resin particleswas maintained. The specific gravity variation of the molded product is0.018 g/cm³ or less and small.

For Comparative Example 1 using the hollow resin particles of ProductionExample 5, which are particles high in the void ratio, the weightreduction ratio is low, and the specific gravity increase ratio is high.Accordingly, it is indicated that the hollow resin particles collapsed.

For Comparative Example 2 or 3 using the hollow resin particles ofProduction Example 6 or 7, which are particles less in the crosslinkablemonomer, the weight reduction ratio is low, and the specific gravityincrease ratio is high. Accordingly, it is indicated that the hollowresin particles collapsed.

For Comparative Example 4 using the hollow resin particles of ProductionExample 8, which are particles not containing a crosslinkable monomer,the weight reduction ratio is high; however, the specific gravityvariation is large. Accordingly, it is indicated that while the moldedproduct was obtained by expanding the unexpanded particles at the timeof molding, a difference occurred in the expansion ratio of theparticles in the molded product.

For Comparative Example 5 using the glass balloons, the weight reductionratio is low, and the specific gravity increase ratio is high.Accordingly, it is indicated that the hollow resin particles collapsed.

From the above results, it was proved that a lightweight molded producthaving a small variation in specific gravity, can be stably molded bythe resin composition of the present disclosure.

REFERENCE SIGNS LIST

-   1. Aqueous medium-   2. Low polarity material-   3. Surfactant-   4. Monomer composition-   4 a. Monomer dispersed in aqueous medium-   5. Oil-soluble polymerization initiator-   6. Shell-   7. Hydrocarbon solvent-   8. Hollow portion-   10. Micelle-   20. Hollow resin particle precursor-   51. Aqueous medium-   52. Surfactant-   53. Monomer composition-   53 a. Monomer dissolved out to aqueous medium-   54. Water-soluble polymerization initiator-   60. Micelle-   60 a. Micelle precursor-   100. Hollow resin particle

1. A resin composition comprising 50 parts by mass to 95 parts by massof a thermoplastic elastomer and 5 parts by mass to 50 parts by mass ofhollow resin particles, wherein the hollow resin particles have a voidratio of from 50% to 85%; wherein the hollow resin particles have ashell containing a resin; and wherein, with respect to 100 parts by massof repeating units constituting the resin, 30 parts by mass to 100 partsby mass of a crosslinkable monomer unit and 0 part by mass to 70 partsby mass of a non-crosslinkable monomer unit are contained as apolymerizable monomer unit.
 2. The resin composition according to claim1, wherein the hollow resin particles do not exhibit a glass transitiontemperature in a range of from 0° C. to 250° C.
 3. The resin compositionaccording to claim 1, wherein the hollow resin particles have avolume-based average particle diameter of from 1.0 μm to 20.0 μm.
 4. Amolded product comprising the resin composition defined by claim
 1. 5.The resin composition according to claim 1, wherein the hollow resinparticles have a particle size distribution (the volume average particlediameter (Dv)/the number average particle diameter (Dn)) of from 1.00 to2.50.
 6. The resin composition according to claim 1, wherein acrosslinkable monomer constituting the crosslinkable monomer unit is atleast one selected from the group consisting of divinyl benzene andethylene glycol di(meth)acrylate.
 7. The resin composition according toclaim 1, wherein the thermoplastic elastomer is at least one selectedfrom the group consisting of a urethane-based elastomer, a styrene-basedelastomer, an olefin-based elastomer, an amide-based elastomer and anester-based elastomer.